1. Field of the Invention
The present invention relates to a communications device, more particularly to a communications device capable of coupling current reduction.
2. Description of the Related Art
Referring to FIG. 1, a portable communications device 9, such as a mobile phone or a notebook computer, includes a first casing 92, and a second casing 91 coupled movably to the first casing 92 via a pivot joint. The second casing 91 is movable relative to the first casing 92 between a covering position and an uncovering position. The second casing 91 is provided with a display. The first casing 92 has a surface provided with keys, etc. A circuit board (not shown) for circuit layout is disposed in the first casing 92, and a hidden antenna 93 is disposed on the circuit board and adjacent to the pivot joint.
According to demands for miniaturization and large screen of the portable communications device 9, metallic materials such as aluminum magnesium alloy have been generally adopted to replace thicker plastic material as casing structures. However, the metallic materials bring about communications problems.
Referring to FIG. 2, the first and second casings 92, 91 adopt a design involving metallic materials. When the second casing 91 is at the covering position, a two-layer metal structure will result in coupling current such that communication through the antenna 93 is affected. For example, the two very-close (0.15 mm apart) metal layers act like a capacitor structure, and thus results in undesired coupling current and a decrease in gain of the antenna 93.